Centrifugal fan

ABSTRACT

A centrifugal fan includes a casing and an impeller module. The casing defines an accommodating space having an air inlet and an air outlet. The impeller module is mounted in the accommodating space for allowing air flow to enter from the air inlet and exit from the air outlet. The impeller module includes a body and a plurality of blade units connected to and annularly distributed along a circumference of the body. Each blade unit has a plurality of blades arranged equi-angularly. A blade spacing which is defined between each adjacent pair of the blades of one of the blade units is different from a blade spacing which is defined between each adjacent pair of the blades of another one of the blade units.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority of Taiwanese Patent Application No.107132408, filed on Sep. 14, 2018.

FIELD

The disclosure relates to a cooling fan, and particularly to acentrifugal fan.

BACKGROUND

The centrifugal fan is one of the commonly used heat dissipatingdevices, the characteristics of the air entering the fan casing from anaxial inlet opening near the shaft of the impeller and being displacedfrom a radial outlet opening at one side of the casing are particularlyadvantageous for the heat dissipation of miniaturized electronicproducts. However, the periodic changes in air pressure will occur inoperation of the centrifugal fan and lead to a source of noise. Theseperiodic changes in pressure are directly related to the number of fanblades, the shape of fan blades, the distribution of fan blades, andeven the rotation speed of the impeller. In particular, when the shapeof the respective blades is the same and the distribution of blade pitchis uniform, the noise from resonance of the fan blades causing troublesin use.

Referring to FIG. 1, an impeller of a conventional centrifugal fan 9 isshown to include a hub 90, a ring member 91 surrounding the hub 90, anda plurality of blades 92 radially extending from the ring member 91. Thearc distances (D) between each two adjacent blades 92, with the sameimaginary circular line as a reference, are designed to exhibitcontinuous variations according to the requirement of reducing noise. Inthe clockwise direction (R) as depicted in FIG. 1, the arc distances (D)between each two adjacent blades 92 gradually decrease from the 12o'clock position and then gradually increase from the 6 o'clockposition. That is, any two adjacent arc distances (D) of these blades 92in the same imaginary circular line are different, such that the blades92 to be rendered by unequal spacing arrangement, thereby reducing theresonance of blades 92 and the noise generated during rotation of thecentrifugal fan 9.

However, in this way of design, if the running test result of thecentrifugal fan is not as expected, it must be re-adjusted theappropriate spacing variation or spacing ratio variation one by one foreach blade 92, so that not only the time and cost of the design arehuge, but also relatively precise processes are required for actualmanufacturing in considering accurately matching the design data,therefore, the costs of design and manufacturing are bound to be high.

SUMMARY

Therefore, the object of the disclosure is to provide a centrifugal fancapable of reducing noise with reduced design and manufacturing costs.

According to the disclosure, a centrifugal fan includes a casing and animpeller module. The casing defines an accommodating space having an airinlet and an air outlet. The impeller module is mounted in theaccommodating space and is rotatable about an axis for allowing air flowto enter from the air inlet and exit from the air outlet. The impellermodule includes a body and a plurality of blade units connected to andannularly distributed along a circumference of the body. Each of theblade units has a plurality of blades that are equi-angularly arrangedalong the circumference of the body. A blade spacing which is definedbetween each adjacent pair of the blades of one of the blade units isdifferent from a blade spacing which is defined between each adjacentpair of the blades of another one of the blade units.

Further, the present disclosure is to provide a variation of thecentrifugal fan capable of reducing noise with reduced design andmanufacturing costs.

Accordingly, this variation of the disclosed centrifugal fan includes acasing and an impeller module. The casing defines an accommodation spacehaving an air inlet and an air outlet. The impeller module is mounted inthe accommodating space and is rotatable about an axis for allowing airflow to enter from the air inlet and exit from the outlet. The impellermodule includes a body and a plurality of blade units connected to andangularly distributed in a rotational direction along a circumference ofthe body. Each of the blade units has a plurality of blades with a bladespacing being defined between each adjacent pair of the blades. For eachof the blade units, the blade spacings among the blades are different,and the blades are arranged in a manner that the blade spacingsincreases in the rotational direction.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent inthe following detailed description of the embodiments with reference tothe accompanying drawings, of which:

FIG. 1 is a top view illustrating an impeller of a conventionalcentrifugal fan;

FIG. 2 is a partly cross-sectional view illustrating a first embodimentof a centrifugal fan according to the present disclosure,

FIG. 3 is a top view of an impeller module of the first embodiment;

FIG. 4 is a top view of an impeller module of a second embodiment of thecentrifugal fan according to the present disclosure; and

FIG. 5 is a top view of an impeller module of a third embodiment of thecentrifugal fan according to the present disclosure.

DETAILED DESCRIPTION

Before the present disclosure is described in greater detail, it shouldbe noted that where considered appropriate, reference numerals orterminal portions of reference numerals have been repeated among thefigures to indicate corresponding or analogous elements, which mayoptionally have similar characteristics.

As shown in FIGS. 2 and 3, the first embodiment of a centrifugal fanaccording to the present disclosure includes a casing 1 which defines anaccommodating space 100 having an air inlet 101 and an outlet 102, andan impeller module 2 which is mounted in the accommodating space 100 andwhich is rotatable about an axis for allowing air flow to enter from theair inlet 101 and then exit from the outlet 102.

In this embodiment, the impeller module 2 includes a body 20, and threeblade units 21 connected to the body 20 and annularly distributed alonga circumference of the body 20. Each of the blade units 21 has aplurality of blades 211 extending from the body 20 away from the axis,and are equi-angularly arranged along the circumference of the body 20.In this embodiment, each adjacent pair of the blades 211 of one of theblade units 21 defines a blade spacing (X1) therebetween, each adjacentpair of the blades 211 of another one of the blade units 21 defines ablade spacing (X2) therebetween, and each adjacent pair of the blades211 of the last one of the blade units 21 defines a blade spacing (X3)therebetween. The blade spacings (X1, X2, X3) among the blade units 21are of different sizes, and the three blade units 21 are arranged in theorder of size of the predetermined blade spacings (X1, X2, X3). With thefull circle around the body 20 as a reference, a blade unit 21 is formedevery 120 degrees, with the blade spacings of the three blade units 21varied from (X1) to (X2) and then to (X3), thereby providingasymmetrically distributed blades 211 as a whole for the impeller module2 of the first embodiment.

Since the blades 211 of the impeller module 2 in the first embodimentare asymmetrically distributed, the noise from resonance during rotationof the impeller module 2 can be reduced. Further, in the design of thefirst embodiment, it is only needed to provide three blade units 21 withdifferent blade spacings (X1, X2, X3), thus obviating the necessity ofadjusting the continuous spacing variation between each adjacent blades92 as illustrated in FIG. 1. Therefore, it can effectively reduce thecosts of design and testing. In addition, because the design isrelatively simple, high-precision processes are not required, therebyreducing the cost incurred in manufacturing.

It should be particularly noted that the first embodiment is describedby taking the form of three blade unit 21 as an example. In actualimplementation, for the consideration of other requirements, four to sixblade units 21 may be designed for an impeller module 2 withoutexcessive difficulty. This can also provide an impeller module 2 withasymmetrically distributed blades 211 in terms of the blade spacing, andachieve the effect of reducing the costs of design and manufacturing.

As shown in FIG. 4, the second embodiment of a centrifugal fan of thepresent disclosure has a structure similar to that of the firstembodiment. The main difference between this embodiment and the firstembodiment resides in the following. The impeller module 2 in thisembodiment includes four blade units 21. The four blade units 21includes two first blade units 2101 with one blade spacing (X4), and twosecond blade units 2102 with a different blade spacing (X5). The firstand second blade units 2101, 2102 are arranged in alternate. In thesecond embodiment, since only two different spacings (X4, X5) are usedin the four blade units 21, the resonance of blades 211 can be preventedin a simpler design to achieve the purpose of reducing noise duringoperation.

As shown in FIG. 5, the third embodiment has a structure similar to thatof the first embodiment. The main difference between this embodiment andthe first embodiment resides in the following. The blade unit 21 in thisembodiment are annularly distributed in a rotational direction (R1)along the circumference of the body 20. Each of the blade units 21 hasfour blades 211 with the blade spacings among the blades 211 beingdifferent. Specifically, each of the blade units 21 has three bladespacings (Y1, Y2, Y3), and the four blades 211 are arranged in a mannerthat the blade spacings (Y1, Y2, Y3) increases in the rotationaldirection (R1). Given that each blade unit 21 has four blades 211 withthree different spacings (Y1, Y2, Y3), in the design of the thirdembodiment, it is only needed to configure the three blade spacings (Y1,Y2, Y3) rather than to adjust the continuous spacing variation betweeneach adjacent blades 92 as illustrated in FIG. 1, so that the cost ofdesign and testing can be effectively reduced as in the firstembodiment, which in turn reducing the cost incurred in manufacturing.

To be particularly noted that the third embodiment is described withrespect to the blade units 21 with four blades 211 as an example, thisembodiment may be implemented depending on the actual requirements withappropriate adjustments. For example, each blade unit 21 has only threeblades 211, or has five blades 211, the intended effect of thisdisclosure can still be achieved without unduly raising the designdifficulty.

In summary, the impeller module 2 of the centrifugal fan 2 of thepresent disclosure is designed in a relatively simple manner to preventthe resonance of blades, thereby reducing the noise during operation,and effectively reducing the costs of design, testing, andmanufacturing.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent, however, to oneskilled in the art, that one or more other embodiments may be practicedwithout some of these specific details. It should also be appreciatedthat reference throughout this specification to “one embodiment,” “anembodiment,” an embodiment with an indication of an ordinal number andso forth means that a particular feature, structure, or characteristicmay be included in the practice of the disclosure. It should be furtherappreciated that in the description, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure and aiding in theunderstanding of various inventive aspects, and that one or morefeatures or specific details from one embodiment may be practicedtogether with one or more features or specific details from anotherembodiment, where appropriate, in the practice of the disclosure.

While the disclosure has been described in connection with what areconsidered the exemplary embodiments, it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. A centrifugal fan comprising: a casing definingan accommodating space that has an air inlet and an air outlet; and animpeller module mounted in said accommodating space and rotatable aboutan axis for allowing air flow to enter from said air inlet and exit fromsaid air outlet, said impeller module including a body and a pluralityof blade units connected to and annularly distributed along acircumference of said body, each of said blade units having a pluralityof blades that are equi-angularly arranged along said circumference ofsaid body, a blade spacing which is defined between each adjacent pairof said blades of one of said blade units being different from a bladespacing which is defined between each adjacent pair of said blades ofanother one of said blade units.
 2. The centrifugal fan as claimed inclaim 1, wherein: said plurality of blade units includes at least threeblade units; the blade spacings among said blade units are different;and said blade units are arranged in the order of size of the bladespacings.
 3. The centrifugal fan as claimed in claim 1, wherein saidimpeller module includes exactly three blade units.
 4. The centrifugalfan as claimed in claim 1, wherein said impeller module includes exactlyfour blade units.
 5. The centrifugal fan as claimed in claim 4, whereinsaid four blade units includes two first blade units with one bladespacing and two second blade units with a different blade spacing, saidfirst and second blade units being arranged in alternate.
 6. Acentrifugal fan comprising: a casing defining an accommodation spacethat has an air inlet and an air outlet; and an impeller module mountedin said accommodating space and rotatable about an axis for allowing airflow to enter from said air inlet and exit from said air outlet, saidimpeller module including a body and a plurality of blade unitsconnected to and annularly distributed in a rotational direction along acircumference of said body, each of said blade units having a pluralityof blades with a blade spacing being defined between each adjacent pairof said blades; wherein, for each of said blade units, the bladespacings among said blades are different, and said blades are arrangedin a manner that the blade spacings increases in the rotationaldirection.
 7. The centrifugal fan as claimed in claim 6, wherein eachblade unit has four blades.